Investigation of Thermal Parameters Effects on the Microstructure, Microhardness and Microsegregation of Cu-Sn alloy Directionally Solidified under Transient Heat Flow Conditions

Abstract

The microstructure and mechanical properties of cast materials are strongly dependent on the thermal history during solidification process. The global casting industry has faced major challenges, i.e., customers increasingly demand completely finished cast parts as well as complexity of casting alloys are rising. Therefore, the previous knowledge the solidification conditions effects on the ascast ingot microstructure and mechanical properties resulting is very useful in the casting industry in order to improve the casting quality. In this present paper, the thermal parameters effects on the microstructure, microhardness and microsegregation of a Cu-20 wt.% Sn alloy under transient heat flow conditions were experimentally investigated. The experimental observations indicate that the tertiary dendritic arm spacing (λ 3), microsegregation and microhardness are affected by the thermal parameters (solidification speed and cooling rate). Solidification speed (S S) associated with increasing cooling rate (R C) are found to contribute to the decreasing tertiary dendritic arm spacing (λ 3). However, cooling rates from 11.36 °C/s to 0.65 °C/s were not found to affect significantly the microhardness along the ingot length. The solute concentration (Sn) in solid region were calculated by Scheil and Clyne-Kurz equation, and used in the predictions of microsegregation profiles. The results calculated by equations, have shown deviations from the experimental data. It is well known that it is very difficult to calculate these concentration profiles using the equilibrium partition coefficient, since frequently castings solidify under non-equilibrium conditions and the solidification process is known as non-equilibrium solidification. For this reason, effect of solidification speed (S S) was considered into equations through effective partition coefficient (k ef) that has been determined for the range of solidification speed experimentally examined between 0.19 and 0.89 mm/s. However, results calculated by Scheil and Clyne-Kurz equation using the effective partition coefficient (k ef), yielded discrepancies from the experimental results. Because of its deviations between calculated and experimental data, an experimental equation with effective partition coefficient (k ef), is considered in present work, showing an excellent agreement with the experimental data.

Microstructure and Microhardness of Directionally Solidified Al-Si Alloys Subjected to an Equal-Channel Angular Pressing Process

“…Over the years, regarding either vertical unidirectional solidification [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][27][28][29][30] or equal-channel angular pressing 19−26, 31, 32 experiments, sundry works have focused on the resulting microstructure. Since microstructure control is a key factor in generating excellent properties in metals and their alloys, determination of parameters which can affect said microstructures is of primary importance.…”

Analysis of Microsegregation in Al-Si-Cu Ternary Alloys: Interdependence of Solute Composition at the Solubility Limit during Non-Equilibrium Solidification

“…On the other hand, the experimental data are not conclusive as to the solidification velocity effect on the concentration profiles. In previous studies presented by Paradela et al 27 and Ferreira et al 33 , the concentration profiles move upward with the increase in solidification velocity. However, binary alloy systems were considered in those works presented by authors.…”

The Effect of the Cooling Rate on the Microstructure and Microsegregation: An Experimental and Numerical Investigation of Solidification in Hypoperitectic Cu − 20 wt.% Sn Alloy

“…The casting with height of 60 mm, was cut for the macrostructural and microstructural analysis. After the solidification experiment, casting was sectioned along its vertical axis, and mechanically polished with abrasive papers and subsequently etched with an acid solution (Ethanol, Ferric chloride and Hydrochloric acid) during 15 s in order to reveal the macrostructure, Paradela et al 35 . After the macrostructural analysis, selected cross section of the solidified specimens at 5, 10 and 15 mm from the mold bottom were polished and etched with a solution of ammonium hydroxide and hydrogen peroxide during 5 s and then etched with an acid solution (Ethanol, Ferric chloride and Hydrochloric acid) during 3 s for micrograph examination.…”